Random Walk Polishing Machine

ABSTRACT

A polishing machine for fine polishing and abrading work configured to employ a random walk theory algorithm to generate the movement pattern of the polishing or abrading element.

RELATED APPLICATIONS

Pursuant to 37 C.F.R. 1.53(b), this is a Continuation in Partapplication to application Ser. No. 15/471,962 filed Mar. 28, 2017.

BACKGROUND OF THE INVENTION

The present invention relates to apparatuses and methods for abrading orpolishing a surface of a workpiece. The abrading or polishing of thesurface of a workpiece is a technique that has many differentapplications in a variety of technical fields, including the productionof semi-conductor devices, optical fiber connectors, mirrors, prisms,lenses and other optical components. It is desirable in these fields,and others, to employ a fine polishing or abrading process that resultsin a particular and specific surface profile and a particular andspecific surface finish, i.e., smoothness. This is typicallyaccomplished by means of a tool that is moved across the workpiece whilethe workpiece is held stationary. Several apparatuses and processes havebeen developed to accomplish the fine movement of a polishing tool inthis manner. For example, U.S. Pat. No. 4,128,968, discloses a polishingapparatus and system whereby two polishing pads are maintained incontact with the surface of the workpiece and are relatively rotated andmoved in a spiraling path around the surface of the workpiece. Anothertechnique is disclosed in PCT No. WO97/00155, which uses a tool that hasa flexible working surface so that the effective area of contact withthe workpiece can be controlled. In these and other prior arttechniques, the tool is usually spun around an axis normal to theworkpiece or parallel to the surface of the workpiece. Since regulartool paths across the same portion of the workpiece invariably creategrooves and ridges in the surface of the workpiece, prior art designshave included apparatuses and methods whereby the abrading tool employsa non-closed orbits movement or a figure-eight movement. This isdesigned to avoid repeated polishing paths over the same area. This isobtained in the case of FIG. 8 movements imposing a lateral displacementof the abrasive platform after cycles of number 8 figure.

However, polishing and abrading machines that employ these movementtechniques are expensive to manufacture as the tools, the tool mounting,and the associated machinery all require a high level of mechanicalprecision.

What is needed therefore are abrading and polishing machines and methodssuitable for use over a wide variety of materials, that is relativelyeasy to operate, that utilizes tool movements designed to ensure thatthe polished surface is free of grooves or ridges, specificallymovements that avoid closed loops, Lissajous figures or path repetition,and that is easy and inexpensive to manufacture.

GENERAL DESCRIPTION

According to the present invention there is provided a novel automatedpolishing apparatus and method configured to move the polishing/abradingtool over the workpiece surface in a pattern that replicates on amacroscopic scale the random motion seen in the Brownian motion ofmicroscopic particles. The apparatus employing such movements can bemanufactured in a variety of ways, but always based on the sameprinciple of random walk. Such a method of employing a random walkmovement of an abrasive platform under or over the pieces to be lapped,abrading or polished being suitable for curved surfaces, plane surfaces,for optical connections, and other precise optical parts includingmirrors, prisms, and lenses. Brownian motion is the random motion ofparticles suspended in a fluid (liquid or gas) resulting from theircollision with the fast moving atoms or molecule in the gas or liquid.This phenomenon has been shown to result in a movement that over timereproduces statistically a normal distribution with a perfectlysymmetrical around the center polishing or abrading configuration.Further, for polishing convex surfaces, as, for example, those found inoptical fiber connectors, the result is that the apex eccentricityequals to zero, which is a desired characteristic in polishing andabrading such objects.

An apparatus is provided whereby a workpiece to be polished and/orabraded is secured to the apparatus and brought into contact to thepolishing platform. The polishing platform is then displaced pursuant tothe movement generated by two independently driven motors operating atseparate frequencies and that are configured such that the twoindependent frequencies result in a movement pathway that is notrepeated. Any groove or ridge in the surface of the workpiece created bythe movement of the polishing tool over a particular path is removed orsmoothed by the movement of the polishing tool in another direction.Further, this random movement will result in no apex eccentricity of asurface being polished. As a result, for convex surfaces, a smoothsurface with no apex eccentricity can be achieved. As a result, when anoptical surface is polished in this manner, namely by this “random walkmovement” of the polisher, it will possess a higher quality and smootherpolished surface than one polished in the manner of currently availableand known polishing machines that employ a FIG. 8 polishing patternand/or orbital polishing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood with reference to theaccompanying drawing wherein like reference numerals refer to likecomponents throughout the several views.

FIG. 1 is a perspective view of an embodiment of the invention.

FIG. 2 is a exploded view of an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in general to a random movement abradingsystem for lapping surfaces of a workpiece.

FIG. 1 shows an embodiment of the invention wherein a polishing unit(200) which comprises a polisher housing (220) that is generallycylindrical in shape and which further comprises a base (130) and case(120), and an upper plate (90). A cushion (140) is provided upon whichthe base (130) rests. The cushion (140) preferably is formed of rubber.A plane platform (60) is disposed along the top of the upper plate (90)and a pad (70), preferably formed of a hard rubber, is disposed alongthe top of the plane platform (60).

Disposed within the housing (220), is a motor assembly (230) comprisinga lower motor (210) secured to the Base (130). A lower eccentric ballbearing (40) is disposed on top of the lower motor (210) along the samevertical axis of the lower motor (210). The motor assembly (230) alsocomprises a second, upper motor (205) with a upper eccentric ballbearing (30) that is disposed on top of the upper motor (205) and alongthe same vertical axis as the upper motor (205). The upper motor (205)is coupled to the lower motor (210) by being attached to the lowereccentric ball bearing (40) by means of a lower flange (50) and an upperflange (55). The motor assembly (230) is positioned within the housingso that the upper eccentric ball bearing (30) is in secured contact withthe underside of the plane platform (60).

FIG. 2 further illustrates the composition—and operation—of the motorassembly. As seen in FIG. 2, the lower eccentric ball bearing (40) isdisposed on top of the lower motor (210). The lower flange (50) isconfigured to secure the lower motor and lower eccentric ball bearing toensure that they both remain disposed within the same vertical axis asthe upper motor (205) and to affect the coupling of the lower motor(210) to the upper motor (205). The lower flange (50) is furtherconfigured with an opening of sufficient size to allow the lowereccentric ball bearing (40) to pass through the lower flange (50) to theupper flange (55). As shown in FIG. 2, the upper flange (55) is securedto the lower flange (50) and is configured with an opening to allow thelower eccentric ball bearing (40) to pass through the upper flange (55)and to be secured by it such the lower eccentric ball bearing will bedisposed on the upper motor (205). The upper flange (55) is furtherconfigured to secure the base of the upper motor (205).

Referring to FIG. 1, a sanding disc (80) is secured to the top surfaceof a rubber pad (70) that stays over a platform, which in thisembodiment is plane and circular, but, it is understood that otherembodiments of the platform within the scope of the invention may notnecessarily be plane and circular. A circular abrading template (150) isprovided that is removably secured to the upper plate (90) and comprisesembedded supports (170) disposed along the surface of the template(150). The embedded supports are configured to allow insertion andretention of a workpiece and further configured to allow the surface ofthe workpiece to be in contact with the sanding disc (80) when theabrading template (150) is secured to the upper plate (90).

The random walk motion of the sanding disc (80) is accomplished by thecombination of the oscillatory motions created by the two motors whenoperated simultaneously. This is accomplished by virtue of the twomotors (lower motor (210) and upper motor (205)) being independentlydriven making each to rotate about their respective axis. As shown inFIG. 2, the lower eccentric ball bearing (40), is acted on by the lowermotor (210) and then imparts its movement to the upper motor (205) byvirtue of it being secured to the upper motor (205) by the upper flange(55) and lower flange (50).

The independent drive of each motor means that each motor can bedriven—and in a preferred embodiment and method they each will bedriven—with different frequencies, non-multiple frequencies andnon-fixed phase frequencies. These frequencies will not only bedifferent but will also form a frequency pair which has no correlationamong themselves. This manner of driving the motors when combined withthe manner in which the motors and the corresponding lower eccentricball bearing (40) and upper eccentric ball bearing (30) are coupled,described above, will compel the sanding disk (80) to vibrate in arandom manner, or more particularly in a manner replicating a randomwalk motion or Brownian motion with no closed loops, Lissajous figuresand no resulting path repetition on the polishing platform.

A shown in FIG. 1, a blocking ring (211) secured to the housing (220)provides further support for the motor assembly (230). As shown in FIG.1, the lower motor (210) is powered by a lower power unit (300) and theupper motor (205) is powered by a separate upper power unit (400). Asdescribed above, in a preferred method, each power unit will apply powerto its respective motor at a different frequency and phase, both ofwhich would be uncorrelated among and between themselves. The resultingoscillatory motions of the motors are transmitted through the motorassembly (230) to create the random movement of the abrading disc (80)described above.

In the embodiment shown in FIG. 1, the abrading template (150) isconfigured to accept and retain optical connectors. In thisconfiguration, a preferred method may include fastening weights (180) tothe connectors to aid in securing the workpiece (160) to holes in theabrading template (170) as well as aiding in maintain proper contactpressure of the workpiece (160) against the abrading disc (80). It isalso contemplated and understood that in this embodiment, the holes ofthe abrading template (170) can be configured to accept a variety ofworkpieces, including, for example, jewelry, optical devices, lenses andvarious metallurgical samples.

The above-described embodiments relate also to methods for performing asurface treatment on a workpiece. The method for performing such asurface treatment would comprise, in a preferred method, generating aseries of random paths which visit all points of a surface area andmoving the surface treatment device along the series of random pathssuch that the surface treatment device passes over all points of theworkpiece. Alternatively, the described invention may encompass anapparatus whereby a machine employs a processing unit to execute apreviously embedded sequence of steps corresponding to a positive andnegative sequence of numbers whose algebraic sum is zero, chosen amongmany sequences of randomly generated numbers. This and other similarmethods are thus described.

Although the present invention has been described herein above withreference to specific embodiments, it will be apparent to a skilledperson in the art that the present invention is not limited to thespecific embodiments and modifications can be made within the spirit andscope of the invention.

1. A machine for polishing a workpiece comprising: a supporting surfacefor securing and supporting the workpiece; a polishing surface forpolishing the workpiece secured to the top of the supporting surface; amounting arrangement for supporting said supporting surface and saidpolishing surface with said mounting arrangement configured in agenerally cylindrical shape and comprising a base, a casing and an upperplate; a movement arrangement for moving said polishing surface withrespect to said supporting surface and across said workpiece with saidmovement arrangement housed within the said casing of said mountingarrangement and comprising a first oscillatory motor secured to saidcasing; a first eccentric ball bearing disposed on top of the firstoscillatory motor and further disposed below and in contact with asecond oscillatory motor disposed above the first oscillatory motor; asecond eccentric ball bearing disposed on top of the second oscillatorymotor; with said mounting arrangement further configured such that thesecond eccentric ball bearing is in contact with the bottom of thesupporting surface; a first power source to operate the firstoscillatory motor and a second power source to the second oscillatorymotor, whereby said polishing surface moves across said workpiece in anumber of random polishing paths generated by the combined operation ofthe first oscillatory motor operating at a first frequency and thesecond oscillatory motor operating at a second frequency.
 2. The machinefor polishing a workpiece of claim 1 wherein the first frequency of thefirst oscillatory motor and the second frequency of the secondoscillatory motor are uncorrelated both between and among them.
 3. Themachine for polishing a workpiece of claim 1 wherein the firstoscillatory motor is coupled to the second oscillatory motor by means ofat least one flange configured to secure the base of the secondoscillatory motor and further configured to secure the first eccentricball bearing to the second oscillatory motor.
 4. The machine forpolishing a workpiece of claim 1 wherein the movement arrangement issecured within the case of the mounting arrangement by means of ablocking ring.
 5. The machine for polishing a workpiece of claim 1wherein the supporting surface is comprised of hard rubber.
 6. Themachine for polishing a workpiece of claim 1 wherein the polishingsurface comprises removable sanding pads.
 7. The machine for polishing aworkpiece of claim 1 wherein the supporting surface comprises embeddedsupports for supporting the workpiece.
 8. The machine for polishing aworkpiece of claim 1 wherein said polishing surface has either a planeor curved shape and said polishing surface executes random-walkmovements across said workpiece wherein said random-walk movements donot replicate a planetary movement, figure-eight pattern or any otherLissajous figures.